The ideal resource for tissue engineering applications is an immunocompatible and pluripotential cell, capable of differentiating into tissues of all three germ layers. Human pluripotential cells can be created using In vitro fertilization technologies (human embryonic stem cells, HESC) [1], from parthenogenesis—the chemical activation of human oocytes (parthenogentically derived embryonic stem cells, PGESC) [2] [3], from isolated human germ cells (primordial germ cells, PGC) [4], or from human amniotic fluid (human amniotic fluid derived stem cells, HAFSC). The advantages of HAFSC are their isolation efficiency, expansion potential and their immunocompatibility, thus, not requiring patients to undergo high dose immunosupressants to prevent immune rejection during cell transplantation.
HAFSC can be isolated from amniotic fluid between 14-18 weeks of gestation and comprise approximately 0.8% to 1.4% of the cells present in amniotic fluid (in submission). These cells are grown in basic medium supplemented with serum, have a high self renewal capacity (>300 population doublings), with a doubling time of less than 36 hours, do not require a feeder layer for undifferentiated expansion, and are autologus with the fetus. In addition, HAFSC maintain their telomeres and normal karyotpye throughout late passaging. Early passage HAFSC express SSEA-4 and OCT-4, but not the full complement of markers expressed by HESC (TRA 1-60, TRA1-81). While they are capable of forming embryoid like bodies, they do not form teratomas when injected into SCID mice. HAFSC can be differentiated in vitro into bone, muscle, fat, endothelia, liver and neurons. When mouse chimeras were created by injecting AFSC into blastocysts, AFSC derived cells were found throughout the embryo.